This invention relates to gaseous light sources subject to microwave excitation. More particularly, the invention relates to an electrodeless discharge resonance lamp for producing light by microwave excitation of gas molecules which can be used in the initiation of chemical reactions by photolysis.
The vacuum ultraviolet region includes ultraviolet radiation characterized by wave lengths between 2000 .ANG. and 2 .ANG.. In the field of vacuum ultraviolet spectroscopy there is a need for light sources producing a continuum of ultraviolet radiation over different portions of the vacuum ultraviolet region and also for producing selective wave lengths of radiation within that region.
One type of ultraviolet light source employs a tuned microwave cavity operating in the continuous wave mode as an exciting source to energize a specified gaseous volume. In this type of light source, an envelope containing an appropriate gas is placed within a tuned microwave cavity. A microwave generator operated at a frequency, typically 2450 mHz, is used to produce the exciting microwaves and the radiation produced within the gas is directed through an appropriate window to a vacuum ultraviolet spectrometer or a chemical reaction vessel or for some other use. With air cooling, such microwave excited light sources may be operated up to a maximum power of about 100 watts. At this power level, the intensity level of radiation which can be generated from the rare gases, typically the argon, xenon, and krypton, is insufficient to serve as a useful high intensity source, especially in the photolysis initiation of chemical reactions. Microwave excitation of gas molecules can produce selective wave lengths of light, the use of which would be advantageous in the initiation of chemical reactions by photolysis because less overall energy would be necessary to initiate the reactions. Thus, there is a need for an electrodeless discharge resonance lamp for producing light by microwave excitation of gas molecules which can be used effectively in the initiation of chemical reactions by photolysis.
Electrodeless discharge resonance lamps in existence today are integrally formed devices which are made of precisely fabricated and fragile glassware. The usefulness of such equipment is limited because it is subject to breakage and because if the window must be cleaned or replaced, the whole device must be thrown out. Thus, there is a need for an electrodeless discharge resonance lamp which is strong enough to stand up to harsh usage such as in a chemical reactor and which can be relatively inexpensively maintained without the necessity of disposal of the entire unit.